Stumping for Democratic nominee Phil Murphy at the Sheraton in Edison, Biden blamed Republicans like President Donald Trump and Gov. Chris Christie for allowing "gutter politics" to rise up in America.

Then, Biden drew attention to the television ad that Guadagno, Christie's lieutenant governor, released Wednesday.

"I just saw it on a laptop," Biden told a crowd of a few hundred Murphy supporters in a ballroom at the hotel. "The return of Willie Horton."

That was a reference to an infamous ad from the 1988 presidential election between then-Vice President George H.W. Bush, the Republican nominee, and then-Massachusetts Gov. Michal Dukakis, the Democrat.

The ad targeted Dukakis for supporting a program in his state in which convicts were allowed weekend passes out prison. Horton, a black convicted killer, raped a woman while out of prison on a furlough. The ad portrayed Dukakis as soft on crime, but critics denounced it as racist.

Bush went on to win the race.

Biden said Thursday "there's a reason" polls show Trump is unpopular in New Jersey and Murphy is ahead in the race to succeed Christie.

"People are sick and tired," Biden said. "They want to raise the standard of dialogue."

Biden added that electing Murphy, a former Goldman Sachs banking executive who spent years as a top Democrat fundraiser, is critical because governors will be on the frontline fighting Trump.

"We have got to send a message all across America and around the world: New Jersey is back and America is on their way back to get rid of this circumstance we have," Biden said.

Murphy has repeatedly said he would help shield undocumented immigrants in New Jersey from Trump's policies. During a debate Tuesday, Murphy said, "if need be," he'd even go as far to make New Jersey "a sanctuary not just city but state."

Guadagno's ad suggests that Murphy would protect people like Jose Carranza, a Peruvian immigrant in the country illegally who was convicted in 2007 in the killings of three friends in a Newark schoolyard. Carranza was previously arrested for raping a child and released on bail.

The ad then references comments Murphy made last month at a town hall co-hosted by NJ Advance Media. Murphy was asked about Carranza and whether he believes state authorities should notify federal immigration officials about undocumented immigrants who are arrested or if they should wait until they are convicted.

Murphy replied that "my bias is going to be having their back" -- a line Guadagno uses in the ad.

But Guadagno's commercial does not include what Murphy said next: that what Carranza did was "heinous" and "we've got to be careful to not extrapolate that and then throw a similar blanket over a whole group of folks."

Numerous other Democrats have denounced Guadagno's ad. State Sen. Richard Codey, D-Essex, said it was "race-baiting," while New Jersey Democratic State Committee Chairman John Currie called it "a load of crap." Murphy himself dismissed the ad as "vile and deceitful."

Guadagno's campaign didn't back down Thursday.

"The ad uses Phil Murphy's own words," Woodcliff Lake Mayor Carlos Rendo, Guadagno's pick of lieutenant governor -- who is Hispanic -- said in a statement. "He wants to make New Jersey a sanctuary state even though three African-American children died at the hands of a child rapist who wasn't deported."

"Kim and I understand we must have the backs of law-abiding New Jerseyans and law enforcement over violent criminals, and we both stand by the ad," Rendo added.